/**
 * 不管是var a = b = 1还是let a = b = 1
 * 都相当于 var/let a = 1; b = 1
 * 所以b会被挂载到全局变量上
 * 
 * var a = 1, b = 1
 * 相当于var a = 1; var b = 1;
 */
let a = b = 1
console.log(a);
console.log(globalThis.a);
console.log(globalThis.b);

